Motor fuel containing octane appreciator



United States Patent 3,036,904 MOTOR FUEL CONTAINING OCTANE APPRECIATORHarry Chafetz, Poughkeepsie, and George W. Eckert and Alfred Arkell,Wappingers Falls, N.Y., assignors to Texaco Inc., New York, N.Y., acorporation of Delaware No Drawing. Filed Sept. 21, 1959, Ser. No.841,033 11 Claims. (Cl. 4463) This invention relates to a hydrocarbonfuel composition of high octane rating. More specifically, it involvesthe discovery that the octane rating of leaded gasoline fuels issubstantially improved by the addition of a particular group of estersof hydroxy substituted heterocyclic oxygen compounds.

The recent increases in compression ratios of automobile engines haveplaced a severe strain on petroleum refiners to produce fuels having theoctane rating demanded by these engines. Premium fuels at the presenttime have research octane ratings between 97 and 100 and it has beenprodicted that premium fuels will have to have octane ratings between105 and 110 five years from now in order to statisfy the octanerequirements of the high compression automotive engines predicted forthat date. In order to produce premium fuels of octane ratings of 95 andabove, it has been necessary for refiners to rely heavily on catalyticrefining operations such as fluid catalytic cracking, catalyticreforming, alkylation and catalytic isomerization.

Catalytic cracking and catalytic reforming, which arev the most widelyused refining operations in the production of high octane fuels, producesubstantial quantities of aromatics; catalytic'cracking also produces asubstantial amount of olefins. It is well known that olefins andaromatics, although possessing high octane ratings, have a poorerresponse to organo-lead compounds such as tetraethyllead than saturatedaliphatic gasoline components. Accordingly, as the aromatic and olefiniccontent of the gasolines have increased to meet the octane levelsrequired by modern automotive high compression engines, the leadresponse of the resulting fuels has diminished. Stated another way, theoctane increment obtainable by the-addition of anorgano-lead compounddecreases as the aromatic and olefin contents of the base fuel increase;The subject invention involves the discovery that the octane rating ofleaded motor fuels containing a substantial concentration of high octanecomponents, that is, aromatic, olefins and mixtures thereof, is markedlyimproved by the addition of a small amount of certain esters ofhydroxydioxane and hydroxytetrahydropyran of prescribed composition.

Incommonly-assigned copending application, Serial No. 689,466, filedOctober 11, 1597 by G. W. Eckert, it is disclosed thathydrocarbylmonocarboxylic acids substantially raise the octane rating of a motorfuel containing an organo-lead anti-knock agent and a substantialconcentration of high octane components which may be aromatichydrocarbons, olefinic hydrocarbons or mixtures thereof. In a series'ofcases filed subsequent to the aforeidentifiedcopending application it isdisclosed that this octane appreciating action in the leaded fuels ofprescribed composition is also possessed by a number of acid derivativessuch as tertiary alkyl esters and acid anhydrides which are converted tohydrocarbyl monoc-arboxylic acids at the conditions prevailing in theengine during combustion. The subject invention involves the discoverythat certain esters of heterocyclic oxygen compounds also have an octaneappreciating action in leaded motor fuel compositions of this type. I

The highoctane hydrocarbon motor fuel of this invention comprises highoctane components including a sub- 3,036,904 Patented May 29, 1962 ice 2stantial concentration of aromatic hydrocarbons, olefinic hydrocarbonsand mixtures thereof, an organo-lead antiknock agent and a hydrocarbylester of a hydroxydioxane Y or a hydroxytetrahydropyran in which theacyloxy radical is on a nuclear carbon atom adjacent to a nuclear carbonatom substituted with at least one hydrogen atom. The nuclear carboncontaining the acyloxy radical is preferably joined to a nuclear oxygenatom. The dioxane and tetrahydropyran esters of prescribed type arepresent in the leaded fuel in a concentration between 0.1 and 5.0 volumepercent.

The action of these hydroxydioxane and hydroxytetrahydropyran esters inappreciating the octane rating of gasoline is characterized by severalunusual features. In the first instance, these esters are ineffective inraising the octane rating of gasoline unless an organo-lead anti-knockagent, normally tetraethyl lead, TEL, is a component of the gasolinemixture. The second unusual characteristic of the action of these estersin appreciating the octane rating of gasolines is the fact that anequivalent concentration of dioxane o1- tetrahydropyran esters causes agreater octane improvement above the 100 octane level than below the 100octane level. The third unusual feature of the action of thesehydroxydioxane and hydroxytetrahydropyran esters is that they appear tohave substantially little effect on the octane rating of a gasolineconsisting essentially of saturated aliphatic hydrocarbons even thoughan organo-lead anti-knock agent is present.

Since organo-lead anti-knock agents exert their greatest octaneappreciation in predominantly saturated para-ffinic base hydrocarbongasolines and have theleast effect on the octane rating of aromatic andolefin-rich gasolines,

the present invention neatly complements tetraethyl lead as an octaneimprover. Hydroxydioxane and hydroxytetrahydropyran esters have theirminimum effect where tetraethyl lead has its maximum effect and exerttheir maximum effect on octane values Where tetraethyl lead has itsminimum elfect.

The novel fuel compositions of this invention have a minimumconcentration of aromatic and/or olefin components of at least 5 volumepercent. The aromatic and/ or olefin components of the motor fuel of theinvention can constitute as high as 100 volume percent thereof butusually comprise between 20 and volume percent. A 5 percentconcentration of aromatics and/or olefins appears to be necessary forhydroxydioxane and hydroxytetrahydropyran esters to exert a significantoctane improvement.

The aromatic components of the motor fuel of the invention are generallysupplied by catalytic reforming or catalytic cracking operations.Catalytic reformate is particularly high in aromatics. The olefincomponents of the motor fuel of the invention are derived either fromthermal cracking, catalytic cracking or polymerization.

The organo-lead reagent necessary for the action of hydroxydioxane andhydroxytetrahydropyran esters as octane improvers is usually atetraalkyl lead compound. Tetraethyl lead is universally used as ananti-knock agent but other tetraalkyl lead compounds such as tetramethyllead, tetrabutyl lead, tetraamyl lead, tetrapropyl lead, etc., possessanti-knock properties and may be used in the fuel compositions of theinvention in conjunction with hydroxydioxane and hydroxytetrahydropyranesters.

The tetraethyl lead mixtures commercially available for automotive usecontain an ethylene chloride-ethylene bromide mixture as a scavenger forremoving lead from the combustion chamber in the form of volatile leadhalides. Tetraethyl lead fluid, the commercial product, comprisestetraethyl lead, ethylene chloride and ethylene bromide, the latter tworeagents being present in 1.0 theory and 0.5 theory, respectively,theory denoting the stoichiometric amount required for reaction with thelead content of the tetraethyl lead.

The organo-lead reagent is present in the fuel compositions of theinvention in concentrations between 0.5 ml. per gallon up to thestatutory limit of organo-lead reagent concentration which, at thepresent time, is 3 ml. per gallon in the case of automotive fuel and 4.6ml. per gallon in the case of aviation fuel. The usual concentration oftetraethyl lead is between 1 and 3 ml. per gallon in automotive gasolineand 2 to 4.6 ml. per gallon in aviation gasoline.

The esters of hydroxydioxanes and hydroxytetrahydropyrans which areeffective in increasing the octane rating of aromatic andolefin-containing leaded gasoline are derived from a hydrocarbylmonocarboxylic acid containing 1 to 30 carbon atoms and ahydroxy-substituted dioxane or a hydroxy-substituted tetrahydropyran inwhich the hydroxy radical is on a nuclear carbon atom adjacent to anuclear carbon containing at least one hydrogen substituent. Theester-containing nuclear carbon atom preferably is attached to a nuclearoxygen atom.

The hydrocarbyl monocarboxylic acids employed in the formation ofeffective ester octane appreciators can be aliphatic, cycloaliphatic oraryl monocarboxylic acids of the general formula: RCOOH wherein Rdenotes a hydrogen atom or a hydrocarbyl radical containing 1 to 29carbon atoms. Preferred monocarboxylic acids employed in the formationof effective hydroxydioxane and hydroxytetrahydropyran esters contain 1to 8 carbon atoms and are either an aliphatic or aryl monocarboxylicacid. Examples of preferred acids used in the formation of the estersare acetic acid, propionic acid, n-butyric acid, valeric acid,n-hexonoic acid, 2-ethylhexanoic acid, benzoic acid and toluic acid.

The esters of the hydroxydioxanes and hydroxytetrahydropyrans must haveat least 1 hydrogen atom on a carbon atom adjacent to the nuclear carbonatom containing the ester group. The ester group preferably is alsoattached to a nuclear carbon atom joined to a nuclear oxygen atom.

Hydroxy substituted 1,3-dioxanes and hydroxy substituted 1,4-dioxanesboth form monocarboxylic acid esters effective as octane appreciators.Hydroxy-l,3-dioxanes useful in the formation of esters effective asoctane appreciators are most readily obtained by condensation ofacetaldehyde and propionaldehyde in the presence of alkaline catalysts.2,4-dimethyl-6-hydroxy-l,3-dioxane is obtained by triinerization ofacetaldehyde and 2,4-diethylmethyl-6-hydroxy-l,3-dioxane is obtained bytrimerization of propionaldehyde. Both of these compounds form effectiveesters since they both contain a hydrogen atom on a nuclear carbonadjacent to the carbon atom containing the hydroxyl substituent and alsohave the ester group attached to a nuclear carbon atom joined to anuclear oxygen atom.

The effective hydroxydioxane and hydroxytetrahydropyran esters can berepresented by one of the three general formulae:

O (R'no o tn")...

til

III

wherein R is a hydrogen atom or a hydrocarbyl radical containing 1-29carbon atoms, R and R are a hydrogen atom or an aliphatic hydrocarbylradical containing 18 carbon atoms, v, w, x, y, and 1 having the values0, 1, or 2, the total of v+w+x+y+z being 8 in Formula I, 6 in Formula IIand 10 in Formula III and at least one R on a carbon atom adjacent tothe nuclear carbon containing the acyloxy radical, RCOO-, being ahydrogen atom.

Example of the effective esters are the following:2-acetoxy-l,4-dioxane, 2-benzoxy-l,4-dioxane, Z-propionoxy-1,4-dioxane,4-acetoxy-l,3-dioxane, 4-lauroxy-1,3-dioxane,2,4-dimethyl-6-acetoxy-l,3-dioxane, 2,4-dimethyl- 6-benzoxy-l,3-dioxane,2,4-dimethyl-6-propionoxy-1,B-dioxane, 2,4-diethyl-5-methyl 6 acetoxy1,3 dioxane, 2,4-diethyl-5-methyl-6-isooctanoxy-1,3-dioxane,2,3-diacetoxy-l,4-dioxane, and 2-acetoxy-3-methyl 1,4 dioxane. Examplesof effective esters of hydroxytetrahydropyran are the following:2-acetoxytetrahydropyran, 2,3-diacetoxytetrahydropyran,2-acetoxy-3-methyltetrahydropyran, 2-propionoxy-4-ethyltetrahydropyran.

It has been theorized that the esters of hydroxydioxane andhydroxytetrahydropyran in which the acyloxy radical is attached to anuclear carbon atom which is adjacent to a nuclear carbon atomcontaining at least one hydrogen atom and is preferably joined to anuclear oxygen atom are effective octane appreciators because underconditions existing during oxidation of the fuel in the internalcombustion engine they decompose to give hydrocarbyl monocarboxylicacids and unsaturated derivatives of dioxane and tetrahydropyran. Esterssuch as 2,4-diisopropyl-5,5- dimethyl-6-acetoxy-1,3-dioxane, an ester ofhydroxydioxane compound formed by trimerization of isobutyraldehyde,which does not contain a hydrogen atom on the nuclear carbon atomadjacent to the nuclear carbon containing the acyloxy radical, isineffective as an octane appreciator. This latter compound cannotreadily decompose on heating to yield a monocarboxylic acid and anunsaturated heterocyclic oxygen derivative.

The hydroxydioxane and hydroxytetrahydropyran esters must be present inthe leaded aromatic and/or olefincontaining compositions of theinvention in a minimum concentration of 0.1 volume percent before asignificant octane appreciation is realized. When the concentration ofthe esters is below 0.1 volume percent, there is no noticeable octaneimprovement in leaded gasolines of prescribed composition. The preferredconcentration of hydroxydioxane and hydroxytetrahydropyran ester fallsbe tween 0.2 and 2.0 volume percent with maximum octane appreciationgenerally being obtained at concentrations between 0.5 and 1.5 volumepercent. Although concentrations of the ester of hydroxydioxanes andhydroxypyrans as high as 5 volume percent may be employed, economicconsiderations preclude the use of such high concentrations. Inaddition, it appears there is a significant decrease in octaneappreciating action after the ester concentration exceeds about 2.0'volume percent.

In Table I there is shown the effectiveness of the by droxydioxane andhydroxytetrahydropyran esters of prescribed composition in raising theoctane rating of a leaded fuel composition containing the prescribedaromatic and/or olefin content. The base fuel employed in Table I had aresearch octane number (RON) of 105, a motor octane number (MON) of 98.5and comprised approximately 10 volume percent n-butane, 40 percentisobutylene-isobutane alkylate, 10 percent pentenes from fluidcatalytically cracked naphtha and 40 percent heavy platformate; the basefuel contained 3 cc. of TEL per gallon. Fluorescent indicator analysis(FIA) of the 105 octane base fuel indicated an aromatic content ofapproximately 35 percent and an olefin content of approximately 6percent; its initial boiling point (IBP) was 90 F. and its end point was367 F.

TABLE I 1,3-dioxane 2.3 Base Fuel+1.0 v. percent 2,4-dimethyl-6-acetoxy-1,3-dioxane 2.5

Base Fuel+0.75 v. percent 2,4-diethyl-5-methyl-6- acetoxy-LS-dioxane 1.3

Base Fuel+0.5 v. percent 2-acetoxytetrahydropyran 2.2

Base Fuel+0.75 v. percent Z-acetoxytetrahydropyran 2.9 Base Fuel+ 1.0 v.percent Z-acetoxytetrahydropyran 2.7 Base Fuel+0.7 v. percent2,3-diacetoxy-l,4-dioxane 2.1 Base Fuel+0.5 v. percent2,4-diisopropyl-5,5-dimethyl-6-acetoxy-1,3-dioxane 0.0

The data in the above table show the effectiveness of esters ofhydroxydioxanes and esters of hydroxytetrahydropyrans in appreciatingthe octane rating of leaded fuels containing the prescribed aromaticand/ or olefinic content. All of the eflective esters contain a hydrogenatom on the nuclear carbon adjacent to the nuclear carbon atomcontaining the ester group and also have the ester group attached to anuclear carbon joined to a nuclear oxygen atom. The ineffective ester,namely 2,4- diisopropyl-5,5 dimethyl-6-acetoxy 1,3-dioxane does not meetthis requirement.

In Table II there is shown the octane appreciating action of estes ofhydoxydioxanes and of hydoxytetahydopyrans of prescribed composition ina commercial premium motor fuel having an RON of 100.9. The premiummotor fuel employed in Table II contained 3 cc. of TEL per gallon andhad an IBP of 89 F. and an end point of 372 F. FIA inticated that itcomprised approximately 50 percent saturated hydrocarbons, 30 percentaromatics and 20 percent olefinic hydrocarbons.

TABLE II Units Improvement in Octane Rating of Premium Fuel by Esters ofHydroxydioxanes and of Hydroxypyrans Increase in RON Base Fuel+0.75 v.percent 2,4-dimethy l-6 acetoxy- 1,3-dioxane 1.3 Base Fuel+0.5 v.percent 2,3-diacetoxy-1,4-dioxane 1.8 Base Fuel+0.7 v. percent2,3-diacetoxy-1,4-d-ioxane 1.1 Base Fuel+0.5 v. percent2,4-diisopropyl-5,5-dimethyl-G-acetoxy-l,3-dioxane 0.0

The data in Table II confirmed the specificity of the octaneappreciating action of hydroxydioxane esters and ofhydroxytetnahydropyran esters to compounds of prescribed composition.Comparison of the data in Tables I and II also show that equivalentconcentrations of the hydroxydioxane esters are more effective in higheroctane base fuels.

Obviously, many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof and, therefore, only such limitations should be imposed asare indicated in the appended claims.

We claim:

1. A hydrocarbon fuel in the gasoline boiling range containing anorgano-lead anti-knock agent, at least 5 volume percent high octanecomponents selected from the group consisting of olefinic hydrocarbons,aromatic hydrocarbons and mixtures thereof and a hydrocarbyl ester of aheterocyclic oxygen compound selected from the group consisting ofesters of hydroxydioxane and hydroxytetr-ahydropyran wherein the acyloxyradical is attached to a nuclear carbon atom joined to a nuclear oxygenatom and a nuclear carbon atom having at least one hydrogen substituent,said ester being present in the concentration between 0.1 and 5.0 volumepercent, which concentration is suflicient to effect substantial octaneappreciation of said leaded fuel.

2. The hydrocarbon fuel according to claim 1 in which said hydrocarbylester is present in a concentration between 0.2 and 2.0 volume percent.

3. The hydrocarbon fuel according to claim 1 in which said organo-leadanti-knock agent is present in a concentration between 0.5 and 4.6 cc.per gallon.

4. A hydrocarbon fuel in the gasoline boiling range containing an alkyllead anti-knock agent in a concentra tion of at least 0.5 cc. pergallon, high octane components selected from the group consisting ofolefinic hydrocarbons, aromatic hydrocarbons and mixtures thereof in aconcentration of at least 5.0 volume percent of said fuel and an esterof a hydrocarbyl monocarboxylic acid containing 1-8 carbon atoms and aheterocyclic oxygen compound selected from the group consisting ofhydroxydiox ane and hydroxytetrahydropyran in a concentration between0.1 and 5 .0 volume percent of said fuel, said ester containing theacyloxy radical attached to a nuclear carbon atom which is joined to anuclear oxygen atom and to a nuclear carbon atom having 'at least onehydrogen substituent.

5. The hydrocarbon fuel according to claim 4 in which the concentrationof said ester is between 0.2 and 2.0 volume percent.

6. The hydrocarbon fuel according to claim 4 in which said high octanecomponents constitute 20-80 volume percent of said fuel.

7. The hydrocarbon fuel according to claim 4 containing 1.0 to 4.6 cc.of tetraethyl lead per gallon.

8. The hydrocarbon fuel according to claim 4 in which said ester is2,4-dimethyl-6-acetoxy-1,3-dioxane.

9. The hydrocarbon fuel according to claim 4 in which said ester is2,4-diethyl-5-methyl-6-acetoxy-1,3-dioxane.

10. The hydrocarbon fuel according to claim 4 in which said ester is2-acetoxy-tetrahydropyran.

11. The hydrocarbon fuel according to claim 4 in which said ester is2,3-diacetoxy-1,4-dioxane.

References Cited in the file of this patent UNITED STATES PATENTS2,321,311 Mottlau et al. June 8, 1943 2,331,158 Arundale et al. Oct. 5,1943 2,360,585 Ross et al. Oct. 17, 1944 2,916,366 Heinrich et al. Dec.8, 1959 FOREIGN PATENTS 929,156 Germ-any June 20, 1955 OTHER REFERENCESImproved Motor Fuels through Selective Blending, by Wagner et al. Paperpresented before the American Petroleum Institute, 22nd Annual Meeting,Nov. 7, 1941, pp. 8-13.

1. A HYDROCARBON FUEL IN THE GASOLINE BOILING RANGE CONTAINING ANORGANO-LEAD ANTI-KNOCK AGENT, AT LEAST 5 VOLUME PERCENT HIGH OCTANECOMPONENTS SELECTED FROM THE GROUP CONSISTING OF OLEFINIC HLYDROCARBONS,AROMATIC HYDROCARBONS AND MIXTURES THEREOF AND A HYDROCARBYL ESTER OF AHETEROCYCLIC OXYGEN COMPOUND SELECTED FROM THE GROUP CONSISTING OFESTERS OF HYDROXYDIOXANE AND HYDROXYTETRAHYTDROPYRAN WHEREIN TEH ACYLOXYRADICAL IS ATTACHED TO A NUCLEAR CARBON ATOMS JOINED TO A NUCLEAR OXYGENATOM AND A NUCLEAR CARBON ATOM HAVING AT LEAST ONE HYDROGEN SUBSTITUENT,SAID ESTER BEING PRESENT IN THE CONCENTRATION BETWEEN 0.1 AND 5.0 VOLUMEPERCENT, WHICH CONCENTRATION IS SUFFICIENT TO EFFECT SUBSTANTIAL OCTANEAPPRECIATION OF SAID LEADED FUEL.